import Prelude hiding (lookup) data Exp = Num
import Prelude hiding (lookup) data Exp = Num Int | Add Exp Exp | Sub Exp Exp | Mul Exp Exp | Div Exp Exp | Var String | Let String Exp Exp | App Exp Exp | Fnc String Exp deriving (Show) type Env = [(String, Val)] data Val = CVal Int | FnVal String Exp Env | Error String deriving (Show) {-Implement a function lookup:: Env -> String -> Val that looks up the value of a variable within a context. This function returns the value of the variable if found and returns an error otherwise. -} lookup :: Env -> String -> Val -- code here-- {- Implement a function eval:: Exp -> Env -> Val to evaluate an expression with an initial context and return a value. Errors occur in the following cases: (a) Left-hand-side of a function application is not a function. (b) Use an undefined variable (c) Arithmetic expression where operand is not a number -} eval :: Env-> Exp -> Val
-- code here --
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